Terminal connection for electrical heating units



F.. KUHN, 1. A. HAND AND 1. e. SPIESS.

TERMINAL CONNECTION FOR ELECTRICAL HEATING UNHS.

' APPLICATION FILED NOV. 14, 1918.

1,400,686, I Patented Dec. 20, 1921.

J 5 6. Spies:

UNITED STATES PATENT OFFICE.

FRANK KUHN, JAY A. HAND, AND JULES G. SPIESS, OF DETROIT, MICHIGAN,

ASSIGNORS TO AMEB1CAN ELECTRICAL HEATER COMPANY, OI DETROIT MICHIGAN, CORPORATION OF MICHIGAN.

TERMINAL conivncrroiv non ELECTRICAL HEATING UNITS.

. new and useful Improvements in Terminal Connections for Electrical Heating Units, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to electrical heating units of that type in which a wire or ribbon of the resistor material is clamped between insulator plates through which the generated heat is conducted to the surface to be heated. The material which has been found most satisfactory for resistors is a metal alloy which forms, when under heat, a protecting coatin of oxid, and as this oxid is of an insu ating nature, difficulty has been experienced in obtaining good electrical connections. Another difficulty arises where the resistor is extended beyond the clamping insulator plates and is exposed to air contact. ing of the air-exposed portion, inasmuch as the rate of heat dissipation through radiation is not as great as that through conduction. Still another difficulty is to form electrical connections with the resistor with out danger of mechanically stressing the latter with danger of breaking.

To overcome these several difficulties we have devised a construction of terminal connection in which the projecting terminal portion of the resistor is reinforced by a member of the same material in electrical and heat conducting contact therewith. This reinforcing member is utilized for the further function of relieving the resistor from tension stresses, being mechanically attached to the insulator member on which the resistor is mounted.

In the drawings we have shown our improvement as applied to the terminal of an electrically heated tool, such as a solderin iron, in whichigure 1 is a longitudinal section through the terminal portion of the tool;

Fig. 2 is an elevation at right angles to Fi 1- i igb is a section illustrating the manner of securing the terminal;

This results in the overheat V Specification of Letters Patent. Patented Dec. 20 1921 7 Application filed November 14, 1918.

Serial No. 262,441.

Fig. 4 is a cross-section through the reinforced terminal.

A is an insulator body, such as a sheet of mica, upon which a resistor ribbon B is wound to form a heating unit. C is the terminal end portion of the resistor, which extends through an aperture in the insulator A and thence outward to the point of attachment to the external terminal contact D. As shown, this portion C extends outward through the hollow handle E of the tool,

the contacts D being mounted at the outer end of said handle. F are the insulator plates covering the resistor upon the insulator A, these beingalso preferably of mica, and G are heat-distributing bodies which are clamped against said insulator plates to cause the transmission of heat by conduction.

With the construction as thus far described, where current is supplied to the unit from the terminals D the heat which is generated equally in all portions of the resistor ribbon will be conducted rapidly from the portions clamped between the insulator plates and in contact with the heatdistributing bodies, while the exposed portion C will accumulate heat and rise in temperature with danger of burning out. To avoid this we surround the portion C by a reinforcing member H, preferably formed of the same material as the resistor, and clamped in contact therewitl Thus the reinforcement H, by largely increasing the cross section of the resistor and proportionately decreasing its. electrical resistance, will limit the heat generation and at the same time by increasing the area of radiating surface will increase the rate of heat dissipation. Consequently the rise of temperature to the danger point is avoided.

There is. however. another defect to be overcome, which is the lack of mechanical strength in the terminal portion of the resistor and the danger of breaking during the operation of attachment to the external electrical connections. The reinforce ment of the resistor alone could not cure this defect, for it would throw even greater stress upon the portion immediately adjacent to the reinforcement. We, therefore, mechanically attach the reinforcement H to the insulator A, which thereby transmits all mechanical stresses from the terminal to the insulator Without passing through the resistor. This mechanical attachment is preferably formedby slitting theinsulator plate at I and forming a hook J at the end of the reinforcement H for engaging the slit. The hook J is preferably of the vfull width of the flat ribbon forming the reinforcement, and this width is sufficient to form a. wrapping about the resistor,

completely inclosing the same. As the re 'inforcement is in contact with the resistor throughout its extent, it will hein good electrical connection therewith and its upper end may, therefore, be attached to the bind- ;ing screw K or other clamping means on the in terminal D. g I

What We claim as our invention is 2-- 'In an electrical heating unit the combination with an insulator, a resistor mounted thereon having a terminal portion extending therefrom, and clamping means for the outer end of said terminal portion,

of a reinforcement formed of a strip me chanically connected to said insulator. and

clamping means, said strip being wrapped about aid terminal portion.

. In testimony whereof we afiix our signs. tures.

FRANK KUHN. JAY A. HAND. JULES e, srmss. 

